This invention relates generally to electrographic copier transfer apparatus, and more particularly to apparatus for electrostatically transferring related transferable images from an image carrier in accurate superposed register on a receiver member.
Recent developments in electrographic copiers have enabled multicolor reproductions (copies) to be produced from multicolor input information. In making such multicolor copies, electrostatic charge patterns respectively corresponding to color separation images of information to be reproduced, are formed on an insulating member (image-carrier). The image-carrier is suitably a continuous web (see U.S. Pat. No. 3,612,677 issued Oct. 12, 1971 in the name of Langdon et al), or a plurality of chips (see U.S. Pat. No. 3,583,807 issued June 8, 1971 in the name of Pollock). The charge patterns are developed with appropriately colored electroscopic marking particles (toner) to form related transferable toner images. Such images are transferred from the image-carrier seriatim to a receiver member in superposed register to form the multicolor reproduction.
The apparatus of the '807 patent has distinct advantages in making multicolor reproductions. For example, in the electrophotoconductive process, the exposure times for forming the respective charge patterns are individually tailored to account for the different spectral characteristics of the image-carrier. Moreover, development of the respective charge patterns can take place simultaneously to improve productivity of the apparatus when compared to apparatus where development of the charge patterns occurs sequentially. However, as is the case with all multicolor reproduction apparatus, registering the receiver member in alignment with the related transferable toner images on the image-carrier for accurate superposed register of the transferred images to such receiver member has proven difficult. Such accurate superposed register is important in that the transferred images must be in accurate register for the colors of the multicolor reproduction to be faithfully reproduced.